---
title: "Initialization Functions"
id: oauth-validator-init
pg_version: "20devel"
---

<a id="oauth-validator-init"></a>

## 50.2. Initialization Functions

OAuth validator modules are dynamically loaded from the shared libraries listed in [`oauth_validator_libraries` (`string`)](runtime-config-connection.md#guc-oauth-validator-libraries). Modules are loaded on demand when requested from a login in progress. The normal library search path is used to locate the library. To provide the validator callbacks and to indicate that the library is an OAuth validator module a function named `_PG_oauth_validator_module_init` must be provided. The return value of the function must be a pointer to a struct of type OAuthValidatorCallbacks, which contains a magic number and pointers to the module's token validation functions. The returned pointer must be of server lifetime, which is typically achieved by defining it as a `static const` variable in global scope. 
typedef struct OAuthValidatorCallbacks
{
    uint32        magic;            /* must be set to PG_OAUTH_VALIDATOR_MAGIC */

    ValidatorStartupCB startup_cb;
    ValidatorShutdownCB shutdown_cb;
    ValidatorValidateCB validate_cb;
} OAuthValidatorCallbacks;

typedef const OAuthValidatorCallbacks *(*OAuthValidatorModuleInit) (void);
 Only the `validate_cb` callback is required, the others are optional.